Sighting apparatus which overcomes trunnion tilt error

ABSTRACT

An artillery gun vehicle, comprising a gun having a barrel, and transverse trunnions which are rigidly and perpendicularly associated with the barrel and which support it for rotation about the axis of the trunnions. A sighting apparatus is positioned substantially distant from the barrel, is rotatable about a transverse horizontal axis and comprises a shaft. An electric motor is operatively connected to the shaft to rotate it about its axis. A sensor is positioned to measure the gun elevation angle as determined by the rotation of the trunnions, and the motor is operatively associated with the angle sensor such that the shaft is rotated through the same angle as the trunnions. The shaft is connected through a knuckle joint to the horizontal axis of the sighting apparatus.

ilnited States Patent Morris et al.

1541 SIGHTING APPARATUS WHICH f 1 OVERCOMES TRUNNION TILT ERROR [72] inventors: Peter Duncan Morris, Knebworth; Brian T. Trayner, Hitchin, both of v England [73] Assignee: British Aircraft Corporation Limited, London, England [22] Filed: Dec. 31, 1969 21 Appl. No.: 889,385

[30] Foreign Application Priority Data [58] Field of Search.....33/48', 89/41 E, 41 AA, 41 T, 89/41 R; 318/696 [56] References Cited UNITED STATES PATENTS 3,048,752 8/1962 Bock ..89/41 T Sept. 5, 1972 794,649 7/1905 Temstrom ..89/4l E 3,327,185 6/1967 Kawada., ..3l8/696 X 561,383 6/1896 Fiske ..33/48 Primary Examiner-Stephen C. Bentley Attorney-Sughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT An artillery gun vehicle, comprising a gun having a barrel, and transverse trunnions which are rigidly and perpendicularly associated with the barrel and which support it for rotation about the axis of the trunnions. A sighting apparatus is positioned substantially distant from the barrel, is rotatable about a transverse horizontal axis and comprises a shaft. An electric motor is operatively connected to the shaft to rotate it about its axis. A sensor is positioned to measure the gun elevation angle as determined by the rotation of the trunnions, and the motor is operatively associated with the angle sensor such that the shaft is rotated through the same angle as the trunnions. The shaft is connected through a knuckle joint to the horizontal axis of the sighting apparatus.

2 Claims, 10 Drawing Figures SIGHTING APPARATUS WHICH OVERCOMES TRUNNION TILT ERROR This inventionrelates to the laying of an artillery gun such as a field gun or howitzer. The gun may be selfpropelled or may be towed from one firing position to another.

When the gun stands at a particular position where the ground is horizontal and level, appropriate azimuth and elevation angles laid off on the gun will ensure accurate aiming of the gun. The angles may be supplied by a distant source, e.g. a command post, because the target at which the gun is aimed may not be visible from the gun position. Should the ground be uneven at that gun position however, the trunnion of the gun will lie tilted, and the'azimuth and elevation angles which were appropriate to the gun when level will then not give accurate aiming of the gun.

This can be shown to be so to an exaggerated degree if one considers the hypothetical case in which the sideways tilt of the vehicle equals 90 to the horizontal when the elevation angles would become azimuth angles.

An example of an existing self-propelled gun and sighting apparatus is shown in the accompanying drawings in which,

FIG. la shows a diagrammatic front view of a self propelled gun with associated sighting apparatus,

FIG. lb shows a diagrammatic plan view of the gun and sighting apparatus shown in FIG. la,

FIG. 10 shows a diagrammatic rear view of the gun and sighting apparatus shown in FIG. la, and

FIG. ld shows a diagrammatic rear view of the gun and sighting apparatus shown in FIG. la when the trunnion axis is inclined to the horizontal. In FIGS. 1b, 10

- and 1d, the vehicle carrying the gun is omitted for clarity of description.

FIG. la of the accompanying drawings shows a gun carrying vehicle 1 standing on horizontal ground. The gun 2 is carried on a trunnion 3 whose axle shaft 4 is extended to one side of the gun trunnion, and a sighting apparatus 11 is rigidly connected to the shaft. With the vehicle standing on level ground and with the gun elevated, an azimuth angle applied to the gun will aim the gun accurately at a target. However, with the vehicle standing at the same place but in a tilted attitude,

and with the gun elevated and rotated in azimuth to the same angles as before, the gun will be incorrectly aimed.

In order to overcome the azimuth error induced by the tilt shown in FIG. 1d, it has been proposed to provide a knuckle joint at the intersection of the vertical axis of the sighting apparatus and the axis of the trunnion axle shaft. FIG. 2a shows a plan view of a gun and sighting apparatus in which such a knuckle is provided, FIG. 2b shows a rear view of the apparatus shown in FIG. 20 when the trunnion axis is inclined to the horizontal, and FIG. 3 shows the sighting apparatus and knuckle joint in greater detail.

Referring to FIGS. 20 and 2b, a gun 12 is provided with a trunnion 13 whose axle shaft 14 is extended to one side of the gun trunnion. A sighting apparatus 21 is coupled to the axle shaft 14 by means of a knuckle joint 16.

The sighting apparatus shown in FIG. 3 comprises a bracket having top and bottom platforms 22 and 23. The two platforms are spaced apart by a vertical wall 24, through which passes a part of the trunnion axle shaft extension 25 carrying an elevation scale 26, and lying on the side of the knuckle joint 16 remote from the gun. On the top platform 22 is mounted an azimuth sight scale 27 whilst the bottom platform 23 carries a pair of bubble levels 28 and 29 positioned at right angles to each other, and with the aid of which the sight axis 30-30 may be maintained vertical. In this condition the shaft extension 25 lies horizontal.

Referring again to FIGS. 2a and 2b, the gun l2 and the sighting apparatus 21 are both mounted in a turret for rotation about a common azimuth axis 31-31. With the trunnion axis tilted, but the sighting apparatus 21 levelled, any elevation applied to the gun not only rotates the shaft extension 25 and the elevation scale 26, but also a component of it is translated into a rotation about the sight vertical axis 30-30. Such rotation causes the sight line to be directed away from its original bearing about the vertical axis 30-30 thereby necessitating a fresh azimuth sight to be taken. The gun will then have to be realigned onto the fresh sight line whereupon the gun laying will be correct.

In both of the known arrangements there is a mechanical interconnection between the gun and the sighting apparatus.

The object of the present invention is to enable a gun to be more easily and accurately aligned upon a target even though the trunnion axis of the gun is not horizontal.

A further object of the invention is to enable gun elevation angles to be applied to a sighting device without the need for a direct connection between the gun trunnion axis and the elevation input shaft of the sighting device.

According to the present invention, the barrel of an artillery gun can be turned about transverse trunnions to set the gun elevation angle, the gun being provided with a sighting apparatus which has a levelling means, and a shaft which lies separate from the gun trunnions but which is arranged to lie inclined to the horizontal at the same angle as do the gun trunnions, the shaft connecting through a nozzle joint to the horizontal-transverse axis of the sighting apparatus, there being means for rotating the shaftabout its own axis through the same angle as that through which the gun-barrel turns about the trunnions during its elevation.

By this arrangement, the sighting apparatus can be operated on by the separate shaft instead of by the gun trunnion shaft and, in the case of a self-propelled gun, can be located anywhere within the vehicle, whilst in the case of a towed gun can be placed in any convenient position, preferably upon the gun traversing mass.

The means for rotating the separate shaft may comprise an electrical tilt-sensitive device attached to the gun to provide an electrical signal representative of the gun elevation, the signal being transmitted to an electric motor which rotates the separate shaft through a gear box. The tilt-sensitive device may be of the type known as an ELECTROLEVEL, which is described in our US. Pat. No. 3,497,950, and its attachment to the gun may be by means of a pivot such that signals representative of elevation and provided to an electrical stepper motor, maintain the tilt sensitive device substantially horizontal, as described in our US. Pat.

No. 3,596,373. The motor driving the gear box which rotates the separate shaft may also be a stepper motor.

Two arrangements embodying the present invention will now be described by way of example, with reference to FIGS. 3, 4, and 6 of the accompanying drawings, of which:

FIG. 3 is the previously referred-to known arrangement of sighting apparatus and knuckle joint;

FIG. 4 is a diagrammatic front view of a selfpropelled gun and sighting device;

FIG. 5 is a diagrammatic front view of a towed gun and sighting device; and

FIG. 6 is an enlarged view of the sighting apparatus shown in FIG. 5.

In the first embodiment shown in FIG. 4, a gun 42 is mounted on trunnions 43 in a turret, and a sighting apparatus 21, also mounted in the turret, is remotely spaced from the gun. The sighting apparatus 21 is of the type shown in FIG. 3, except that the shaft 44 does not extend to the knuckle joint 16; a separate shaft 45 replaces it and is mounted in bearings 61 on a gear quadrant 62. The teeth of the quadrant 62 mesh with a gear 63 which is on the output shaft of a gear box (not shown) driven by a stepper motor 64. The motor 64 receives driving signals from a distant reading level 65 which is mounted on the gun trunnion so as to supply electrical signals representative of the tilt angle 66 of the trunnion. The stepper motor 64 sets the angle of the shaft 45 to be the same as the trunnion tilt angle 66.

The shaft 45 in the bearings 61 is rotated around an axis which lies parallel to the turret axis, to maintain the shaft 45 parallel to the trunnion shaft 44. This can be achieved by any known devices, for example synchronous motors.

A second distant reading level 67 on the gun provides elevation signals to a second stepper motor 68 and gear box (not shown), the output of which is in mesh with a gear 71 on the end of the shaft 45. The second motor 68 applies to the shaft an angular rotation corresponding to gun elevation angle.

In operation, with the vehicle stationary the turret is swung, and the sighting device is levelled and is sighted onto a target or is aligned onto a bearing. The appropriate tilt angle 66 is automatically applied to the shaft 45 by the first level 65 and the associated stepper motor 64. The gun is elevated to the necessary angle depending on range of target, etc., and the second distant reading level 67 supplies a signal to the second stepper motor 68 to cause the shaft 45 to rotate, thereby altering the sighting angle about the vertical axis 3030 of the sight. The sight, coupled to the gun for rotation about the vertical axis 3030, is then resighted onto the target or is realigned onto the correct bearing, and the gun is thereby re-aligned accordingly. With this arrangement the sighting apparatus may be placed in the vehicle but remote from the turret.

The above proposal considers only sideways tilt. Fore and aft tilt can be catered for in a similar manner.

In a modification of FIG. 4, the shaft 45 is mounted in bearings supported by the turret structure. All parts of the turret are tilted by the same amount and provided the sighting apparatus is in the turret, the shaft 45 attached to it is also tilted. In this case, the first distant reading level 65, the first stepper motor 64 and the quadrant 62 are omitted; the sighting apparatus still requires to be levelled before use.

In the second embodiment shown in FIGS. 5 and 6, a gun barrel 101 is mounted on a trunnion 102-supported by a cradle 103. The cradle 103 includes a traverse mechanism 104 for allowing a small angle of azimuth adjustment to be applied to the gun barrel relatively to the carriage 105. A sighting device 21, which is carried in a mounting 106 supported on the gun cradle 103, comprises top and bottom platforms 112 and 113 spaced apart by a vertical wall 114. Through the wall 114 passes a shaft 115 carrying an elevation scale 116. A knuckle joint couples the shaft to a separate shaft 117 which is maintained at the same tilt angle as the gun trunnion axis. On the top platform 112 is mounted an azimuth sight scale 118 whilst the bottom platform 113 carries a pair of bubble levels, one of which is shown as 121, positioned at right angles to each other and with the aid of which the sight axis 119-119 may be made vertical.

The shaft 117 is mounted in bearings 122 on the gun cradle. A distant reading level on the gun, provides elevation signals through a cable 141' to a stepper motor 142 and a gear box (not shown). The output of the gear box drives a pinion which is in mesh with a gear 143 on the end of shaft 117, and thereby applies to the shaft an angular rotation corresponding to the gun elevation angle.

In operation, the gun having zero elevation angle is positioned in the general firing azimuth direction, then the sighting device is levelled and aligned onto the target, i.e. the azimuth angle thereof. The shaft 117 has the same tilt angle as the trunnion axis. The gun is then elevated to the necessary angle depending on range of target, etc., and the distant reading level 140 supplies a signal to the stepper motor 142 causing the shafts 117 and 115 to rotate, and thereby alter the sighting angle of the sight (i.e. azimuth) about its vertical axis 119- 1 19.

The sight is then realigned onto the correct azimuth bearing by rotating the gun and sight assembly about the gun azimuth axis by means of the traverse mechanism 104.

In case of electrical power failure, the separate shaft may be rotated by hand through an appropriate mechanism.

We claim:

1. An artillery gun vehicle, comprising a gun having a barrel, transverse trunnions which are rigidly and perpendicularly associated with said barrel and which support said barrel for rotation about the axis of the trunnions, a sighting apparatus which is physically separate from said barrel, said sighting apparatus being rotatable about a transverse horizontal axis and comprising a shaft, a first electric motor which is operatively connected to said shaft to rotate it about its axis, said shaft carrying a gear quadrant which is rotatable in the plane of the face of the quadrant by said first motor, said shaft also being rotatable about its axis by said second motor, sensing means positioned to measure the gun elevation angle as determined by the rotation of said trunnions, said motor being operatively associated with said angle-sensing means whereby said shaft is rotated through the same angle as said trunnions, said shaft being connected through a knuckle joint to the horizontal axis of said sighting apparatus.

2. An artillery gun vehicle, comprising a gun having a barrel, transverse trunnions which are rigidly and perpendicularly associated with said barrel and which sup,

nected through a knuckle joint to the horizontal axis of said sighting apparatus, a second angle sensing means positioned to measure the angle of attitude of the axis of said trunnions relatively to the horizontal, and a second electric motor operatively associated with said second sensing means and adapted to tilt said shaft so that its axis has the same attitude as said trunnions, said shaft carrying a gear quadrant which is rotatable in the plane of the face of the quadrant by said first motor, said shaft also being rotatable about its axis by said second motor. 

1. An artillery gun vehicle, comprising a gun having a barrel, transverse trunnions which are rigidly and perpendicularly associated with said barrel and which support said barrel for rotation about the axis of the trunnions, a sighting apparatus which is physically separate from said barrel, said sighting apparatus being rotatable about a transverse horizontal axis and comprising a shaft, a first electric motor which is operatively connected to said shaft to rotate it about its axis, said shaft carrying a gear quadrant which is rotatable in the plane of the face of the quadrant by said first motor, said shaft also being rotatable about its axis by said second motor, sensing means positioned to measure the gun elevation angle as determined by the rotation of said trunnions, said motor being operatively associated with said angle-sensing means whereby said shaft is rotated through the same angle as said trunnions, said shaft being connected through a knuckle joint to the horizontal axis of said sighting apparatus.
 2. An artillery gun vehicle, comprising a gun having a barrel, transverse trunnions which are rigidly and perpendicularly associated with said barrel and which support said barrel for rotation about the axis of the trunnions, a sighting apparatus which is physically separate from said barrel, said sighting apparatus being rotatable about a transverse horizontal axis and comprising a shaft, a first electric motor which is operatively connected to said shaft to rotate it about its axis, sensing means positioned to measure the gun elevation angle as determined by the rotation of said trunnions, said motor being operatively associated with said angle-sensing means whereby said shaft is rotated through the same angle as said trunnions, said shaft being connected through a knuckle joint to the horizontal axis of said sighting apparatus, a second angle sensing means positioned to measure the angle of attitude of the axis of said trunnions relatively to the horizontal, and a second electric motor operatively associated with said second sensing means and adapted to tilt said shaft so that its axis has the same attitude as said trunnions, said shaft carrying a gear quadrant which is rotatable in the plane of the face of the quadrant by said first motor, said shaft also being rotatable abOut its axis by said second motor. 